Rouhani warned that Iran was ready to walk out of the deal -- which saw the lifting of most international sanctions in return for curbs on its nuclear programme -- if Washington persisted. ...
"If they want to go back to that experience, definitely in a short time -- not weeks or months, but in the scale of hours and days -- we will return to our previous situation very much stronger."
So according to Iran, the deal can be undone in a matter of hours--so the deal didn't dismantle anything of importance; and Iran claims their position will be much stronger when they escape the deal--so the deal has allowed Iran to make progress on nuclear technology.
And this is what the Obama administration called smart diplomacy.
UPDATE: Four ways to kill the deal: appeal to the sainted international community that Iran is still going nuclear; declare Iran in noncompliance; submit the deal as a treaty to the Senate where it will be defeated; or strictly enforce the deal by inflicting harsher penalties.